Biomedical subjects

R Balling

Publications and source records attributed to R Balling.

98 records · Page 6Linked to original sources

PubMed1985

Direct effects of nicotine on rabbit preimplantation embryos.

The effects of various concentrations of nicotine on the in vitro development of 1-cell rabbit preimplantation embryos and on the DNA-synthesis of 4-day-old rabbit blastocysts are investigated. Exposure of rabbit preimplantation embryos to concentrations of nicotine higher than 1 X 10(-3) M results in a marked decrease in the in vitro development and in DNA-synthesis. Concentrations of nicotine below 1 X 10(-3) M have no effect on these early embryos. It can be concluded that the concentrations of nicotine which exert a direct embryotoxic effect are higher than the concentrations that may be expected in the blood circulation of humans considered to be "normal smokers".

Animals↗

PubMed1985

Oxidative and conjugative metabolism of diethylstilbestrol by rabbit preimplantation embryos.

Five- and six-day-old rabbit preimplantation embryos were found to be capable of metabolizing [3H]diethylstilbestrol (DES) in vitro. Based on the analysis of the metabolites formed during a 24-hr incubation period we conclude that these early stage embryos do have active monooxygenase and conjugative activity. The monooxygenase seems to be specific to this early stage of embryonic development.

Animals↗

PubMed1985

Insertion of a bacterial gene into the mouse germ line using an infectious retrovirus vector.

Using a Moloney leukemia virus vector containing the bacterial neo gene, we demonstrate that retrovirus vectors can be used to introduce genes into the mouse germ line. Infection of preimplantation embryos with the vector MLV-NEO.1 resulted in integration of neo sequences in approximately equal to 10% of the progeny mice. One of these animals, mouse F.2, contained approximately six MLV-NEO.1 proviruses at independent integration sites, each present at less than a single copy per cell. This mosaic mouse transmitted one of these proviruses to her offspring, producing a line of transgenic mice carrying a full-length, unrearranged MLV.NEO.1 provirus at a single chromosomal integration site. Mice homozygous at this MLV-NEO.1 locus have also been produced. No expression of the neo gene has been detected in the transgenic mice, either by screening of primary bone marrow or lung cells for resistance to G418 or by RNA transfer blot analysis of RNA from several tissues. In addition, the neo gene was found to be extensively methylated in the transgenic mice; however, treatment of primary cells with 5-azacytidine did not induce G418 resistance. The inactivity of the MLV-NEO.1 provirus in transgenic mice and potential means of eliciting neo expression under these conditions are discussed.

Animals↗

PubMed1984

Asparagine and glutamine metabolism in chicks.

In a series of four experiments, asparaginase and glutaminase activity was measured in liver and kidney tissue of 7- to 19-day-old male broiler chicks. In Experiment 1, chicks were fed purified amino acid diets with 14.8 and 44.6% protein equivalents (PE) with 1, 3, or 5% added sodium bicarbonate. In Experiments 2, 3, and 4 the chicks were fed a 23% protein basal control diet, basal diet containing 5% ammonium chloride, and basal diet containing 5% ammonium chloride with 5 or 10% sodium bicarbonate, asparagine, or glutamine. In Experiments 2 and 4 the chicks were also fed 25, 50, or 75% protein-isolated soy-purified diets. The 44.6% PE diet increased liver and kidney asparaginase activity in chicks as compared to chicks fed a 14.8% PE diet. The addition of sodium bicarbonate to the 44.6% PE amino acid diet decreased the kidney asparaginase activity equivalent to kidney asparaginase activity of chicks fed the 14.8% PE diet. Asparaginase activity increased 4-fold in the kidneys of chicks fed the 23% protein basal diet containing 5% ammonium chloride and the pH of the urine from the chicks was 4.9. Chicks fed basal diets with 5% ammonium chloride plus 10% sodium bicarbonate or asparagine had the same kidney asparaginase activity and urine pH as chicks fed the 23% protein basal control diet. Glutamine added to chick diets containing 5% ammonium chloride did not decrease the kidney asparaginase activity or the urine acidity. Liver asparaginase activity was not increased in acidotic chicks fed diets with 5% ammonium chloride. The asparaginase activity of liver and kidney tissue were both significantly increased in chicks fed 75% protein-isolated soy purified diets and the pH of their urine was 5.6. The increase in liver asparaginase of chicks fed 75% protein or 44.5% PE diets was probably due to an endocrine gluconeogenic response producing increased catabolism of the majority of amino acids. The increase in kidney asparaginase of chicks fed 75% protein, 44.5% PE diets, and 23% protein basal diets with 5% ammonium chloride was primarily related to metabolic acidosis. Phosphate-dependent glutaminase (PDG) activity was localized in chick kidney mitochondria and was heat sensitive (55 C for 30 sec). The phosphate-independent glutaminase (PIG) activity was primarily localized in chick kidney mitochondria but was stable to a temperature of 55 C for 30 sec.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗

PubMed1981

Effect of dietary asparagine and protein-equivalents in crystalline amino acid diets on asparagine metabolism in chicks.

The effect of dietary asparagine and protein-equivalents from crystalline amino acid mixtures upon asparagine metabolism in chicks were studied. Liver and kidney asparaginase activities were significantly increased in chicks fed 44.6% protein-equivalents compared to chicks fed the Illinois chick standard amino acid mixture containing 14.8% protein-equivalents. The asparagine synthetase activity in chick liver and kidney was not significantly changed by protein-equivalents or dietary asparagine. Liver and kidney asparaginase activities in chicks fed 14.8% protein-equivalent standard diets were decreased with increasing levels of dietary asparagine (0,2 and 6%). Kidney asparaginase activities in chicks fed 44.6% protein-equivalents also were decreased with increasing levels of asparagine but liver asparaginase in these chicks was not changed with dietary asparagine. The plasma asparagine concentration was dependent on the amount of dietary asparagine and protein-equivalents. Dietary asparagine increased plasma asparagine in chicks fed 14.8 and 44.6% protein-equivalent diets but plasma asparagine in chicks fed the 14.8% protein-equivalent diet plus 6% asparagine was 3.5 times higher than plasma asparagine in chicks fed the diet containing 44.6% protein-equivalent plus 6% dietary asparagine. Plasma asparagine in chicks fed the 44.6% protein-equivalent diet with 6% asparagine was reduced due to increased asparaginase activity.

Animals↗

PubMedDate not supplied

Tailchaser (Tlc): a new mouse mutation affecting hair bundle differentiation and hair cell survival.

We have undertaken a phenotypic approach in the mouse to identifying molecules involved in inner ear function by N-ethyl-N-nitrosourea mutagenesis followed by screening for new dominant mutations affecting hearing or balance. The pathology and genetic mapping of the first of these new mutants, tailchaser (Tlc), is described here. Tlc/+ mutants display classic behavioural symptoms of a vestibular dysfunction, including head-shaking and circling. Behavioural testing of ageing mice revealed a gradual deterioration of both hearing and balance function, indicating that the pathology caused by the Tlc mutation is progressive, similar to many dominant nonsyndromic deafnesses in humans. Based on scanning electron microscopy (SEM) studies, Tlc clearly plays a developmental role in the hair cells of the cochlea since the stereocilia bundles fail to form the characteristic V-shape pattern around the time of birth. By young adult stages, Tlc/+ outer hair bundles are grossly disorganised although inner hair bundles appear relatively normal by SEM. Increased compound action potential thresholds revealed that the Tlc/+ cochlear hair cells were not functioning normally in young adults. Similar to inner hair cells, the hair bundles of the vestibular hair cells also do not appear grossly disordered. However, all types of hair cells in the Tlc/+ inner ear eventually degenerate, apparently regardless of the degree of organisation of their hair bundles. We have mapped the Tlc mutation to a 12 cM region of chromosome 2, between D2Mit164 and D2Mit423. Based on the mode of inheritance and map location, Tlc appears to be a novel mouse mutation affecting both hair cell survival and stereocilia bundle development.

Animals↗

PubMedDate not supplied

Degree of methylation of transgenes is dependent on gamete of origin.

Data derived from both pronuclear transplantation experiments and classical genetic experiments indicate that the maternal and paternal genetic contributions to the mammalian zygote nucleus do not function equivalently during subsequent development. These observations have been interpreted as resulting from differential 'genome imprinting' during male and female gametogenesis. The molecular mechanism responsible for genome imprinting is unknown, but data gathered to date require that the mechanism fulfill at least four criteria: (1) the imprint must be physically linked to the pronucleus; (2) the imprint must persist through DNA replication and cell division; (3) the mechanism must be capable of affecting gene expression; and (4) the mechanism must be capable of switching the identity of the imprint from one sex to the other in successive generations. One molecular mechanism which could satisfy the first three criteria is differential DNA methylation during gametogenesis itself, or before formation of the zygote nucleus during embryogenesis. We present data indicating that the methylation patterns of exogenous DNA sequences in transgenic mice can be changed by switching their gamete of origin in successive generations. These data suggest that DNA methylation can also satisfy the fourth criterion for an imprinting mechanism.

Animals↗

PubMedDate not supplied

Enu mouse mutagenesis: generation of mouse mutants with aberrant plasma IgE levels.

BACKGROUND: The ENU Mouse Mutagenesis Project aims at a large-scale, systematic production of mouse mutants using the alkylating agent ethyl-nitrosourea (ENU). Offspring of mutagenized mice are subjected to a multiparameter screen to detect alterations in various phenotypes with the ultimate goal of identifying novel genes relevant for the expression of the phenotype. Using this approach, we have analyzed plasma IgE concentrations to identify mouse mutants with aberrant plasma IgE levels. METHODS AND RESULTS: ENU-mutagenized male C3HeB/FeJ were mated to wild-type females to produce F1 offspring. F1 animals were analyzed for alterations in their plasma IgE concentrations that showed a dominant mode of inheritance, or bred further to screen for recessive phenotypes. Plasma IgE concentrations were determined by ELISA and a normal range for plasma IgE was established using C3HeB/FeJ wild-type animals. So far we have tested 6568 F1 animals. Repeated testing confirmed a stable aberrant IgE phenotype in 124 animals. To confirm the genetic basis of the observed phenotype, these mice were subjected to confirmation crossing. Currently we have established 9 independent mutant mouse lines (3 with high plasma IgE and 6 with plasma IgE below detection limit) that have been genetically confirmed and additional 24 variant mouse lines are currently undergoing confirmation testing. CONCLUSION: ENU mouse mutagenesis allowed us to generate and identify mouse mutants with aberrant plasma IgE levels, which may be used to characterize novel genes involved in IgE regulation and may serve as animal models for IgE-mediated diseases.

Alkylating Agents↗